PARENT SESSION
Poster Session #35: Reproductive Ecology.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Fragmented Populations of Opuntia streptacantha (Cactaceae) .
MUŅOZ URIAS, ALEJANDRO*,1, PALOMIN HASBACH, GUADALUPE2, VELAZQUEZ, ARMANDO GARCIA3, TERRAZAS, TERESA4, PIMIENTA BARRIOS, EULOGIO5, HUERTA MARTINEZ, MARTIN, 1 UNIVERSIDAD DE GUADALAJARA, GUADALAJARA, JALISCO, MEXICO2 UNIVERSIDAD NACIONAL AUTONOMA DE MEXICO, MEXICO, DISTRITO FEDERAL, MEXICO3 COLEGIO DE POSGRADUADOS, TEXCOCO, MEXICO, MEXICO4 COLEGIO DE POSGRADUADOS, TEXCOCO, MEXICO, MEXICO5 UNIVERSIDAD DE GUADALAJARA, GUADALAJARA, JALISCO, MEXICO
ABSTRACT- Sexual compatibility, morphological variation and chromosome numbers were analyzed in two isolated populations of Opuntia streptacantha growing in the south west part of the Chihuahuan desert. The main aim was to evaluate if reproductive isolation and morphological variations in isolated populations of O. streptacantha might be induced by fragmentation that causes reduction of gene flow. Cross pollinations revealed a certain degree of sexual isolation during the progamic phase, as indicated by both reduced pollen grain germination and reduced frequency of pollen tubes growing to the base of the style. Interpopulational cross pollination showed 35 to 17 pollen tubes whereas control and intrapopulational self pollination showed 74 and 73 pollen tubes at the base of style 24 h after pollination treatment. Similar tendencies were observed in pollen tubes arriving at the ovules 72 h after pollination because interpopulational cross pollination treatments showed 33 to 34 tubes and control and intrapopulational self pollination 98 and 81 tubes respectively. The average seed set was higher in control and intrapopulational self pollinations with 53 and 58 seed set, whereas interpopulational cross pollination showed 32 to 21 seed set. Multivariate statistical analysis was used to group individuals according to morphological and anatomical similarity. Individuals grouped according to populations and were associated with morphological and anatomical characters linked to strength. No observed different chromosome numbers between populations can be attributed to low fertility between populations.
KEY WORDS: Opuntia streptacantha , outbreeding depression, sexual incompatibility, habitat fragmentation